The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
An engine generates torque through the combustion of fuel, and a part of the fuel is exhausted as thermal energy. In particular, coolant absorbs thermal energy while circulating through the engine, a heater and a radiator, and releases the absorbed thermal energy to the outside.
When the coolant temperature of the engine is low, the viscosity of oil may increase while raising friction and fuel consumption. Then, the temperature of exhaust gas may slowly rise to increase the time required for activating a catalyst, and the quality of exhaust gas may be deteriorated. Furthermore, quite a long time may be required until the function of the heater is normalized.
When the coolant temperature of the engine is excessively high, knocking may occur. When ignition timing is adjusted in order to suppress the occurrence of knocking, the performance may be degraded. Furthermore, when the temperature of lubricant is excessively high, lubrication may not be normally performed.
Thus, a coolant control valve unit is applied to control a plurality of cooling elements through one valve. The coolant control valve unit may maintain the temperature of coolant at a high temperature in a specific portion of the engine while maintaining the temperature of coolant at a low temperature in another portion of the engine.
The coolant control valve unit controls coolant which circulates through each of the engine (oil cooler, heater and EGR cooler), the radiator and the like, thereby improving the entire cooling efficiency of the engine and reducing fuel consumption.
Therefore, a coolant temperature sensor is used to sense coolant temperature at a predetermined position, a target coolant temperature is set according to an operation condition, and the coolant control valve unit is controlled according to the target coolant temperature.
In particular, coolant temperature sensors may be arranged to sense coolant temperature at a coolant entrance and coolant exit of the engine and a radiator exit. According to the coolant temperatures sensed by the coolant temperature sensor, the valve opening degree of the coolant control valve unit may be controlled.
Recently, research has been conducted on a method which minimizes the number of coolant temperature sensors, senses coolant temperature at a predetermined position using an existing coolant temperature sensor, calculates coolant temperature at a predetermined position, and rapidly changes the valve opening degree of the coolant control valve unit using the sensed coolant temperature and the calculated coolant temperature, when the target coolant temperature was changed.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the disclosure and therefore it may contain information that does not form the prior art that is already known to a person of ordinary skill in the art.
Further areas of applicability will become apparent from the description provided herein. It should be understood that the description and specific examples are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure.